MX2010010467A - Positioning, detection and communication system and method. - Google Patents

Abstract

A positioning, communication, and detection system designed to provide a three dimensional location of an object, navigation tools, and bidirectional surface-to-subsurface communications, and methods of using the system. The system can include one or multiple transmitters comprising electromagnetic beacons, software defined radio receivers with an associated processing unit and data acquisition system, and magnetic antennas. The system may use theoretical calculations, scale model testing, signal processing, and sensor data.

Description

POSITIONING, DETECTION AND COMMUNICATION SYSTEM This application is a partial continuation of U.S. Patent Application Serial No. 11 / 640,337, filed December 18, 2006, which claims the benefit of US Provisional Patent Application Serial No. 60 / 750,787, filed on December 16, 2005, whose full description of each of them is incorporated herein by reference.

GOVERNMENT RIGHTS Part of the work done during the development of this invention has employed funds from the United States government. The United States government could have certain rights in the invention.

TECHNICAL FIELD OF THE INVENTION The described modalities generally refer to methods and devices corresponding to a positioning, detection and communication system.

BACKGROUND OF THE INVENTION The generation of geological maps and geophysical exploration on the Earth's surface are mature sciences with a history of technological improvements that have improved fidelity in the understanding of the Earth, above and below the surface. However, when conventional techniques are used in an underground environment, geolocation has represented a challenge that takes concepts from replacement analysis techniques for geolocation instrumentation and geological contacts and can actually limit the effectiveness of the technologies used.

The conventional systems of generation of maps and exploration, such as the Global Positioning System (GPS), determine the location of objects using satellite signals. However, there is a longstanding problem with determining the location of personnel and equipment within, for example, underground facilities without the use of exploration. To date, this problem has not been solved due to the difficulty of signaling / communication between the earth's surface and underground facilities / caverns / mines, as well as the complexity of electromagnetic propagation within the Earth.

Very low frequency systems with lower fidelity are currently under development in Europe to support communications for rescue operations in caves. The systems they only obtain a position of depth when the communication system is used underground. These communication systems are effective up to 600 m and occasionally up to 1,200 m. The systems are also used to locate underground transmitters at comparable depths. In controlled experiments, they achieved an accuracy of 2% in the horizontal position and only 5% in depth.

The typical means for providing the basic time synchronization between a transmitter and the receiver used for navigation purposes has been either (1) providing a uniform time radio reference signal from a separate source (GPS or VLF signal). ) or (2) providing each transmitter and receiver with their own highly stable and accurate timing mechanism that then synchronize mutually at the beginning of the period of interest. In underground environments, GPS and VLF signals are either unavailable or unreliable. Providing each device with its own stable time base could be costly, difficult and wasteful of the limited electrical energy that is available.

Normal wireless radio frequency communications to / from a subsurface receiver by a surface transmitter have not been available due to the electrical properties of the soil, soil and rock. Communications beyond a depth of 100 meters are particularly difficult. A system that provides wireless contact between underground locations and surface locations would be desirable. In particular, such a system could provide accurate positioning, detection and communication on the subsurface and the surface of the Earth.

BRIEF DESCRIPTION OF THE INVENTION The system provides a means for the determination of locations in the subsoil, the determination of underground masses and surface communications to the subsurface. This development is made possible through the assembly of detector technologies and processing capabilities that are currently evolving in the state of the art in various fields.

The system can provide individuals and equipment that move within a space, either above or below the earth, the ability to know its location in three dimensions. The system identifies the location of an object by applying theoretical calculations, as well as innovative demonstrations of technology, including state-of-the-art signal processing, fusion of multiple sensor data, and unique operating concepts, including magnetic headlights and special Radio Receivers defined by Software. (SDR) to determine the location of an object, above or below the ground. The return channel communication capability is provided.

An example of system mode uses multiple transmitters on the surface, in the vicinity of an underground space, to provide magnetic headlights. Signal processing can be supplemented with distant signals of opportunity, both cooperative and non-cooperative. The receiver of SDR transported underground can measure angles between different transmitters. The locations of the surface transmitters can be determined when they are deployed and the magnetic radiation field can be calculated so that the location of the underground receivers can be determined.

An inertial guidance unit may be included as part of the processing unit, to provide a stable reference as a provisional navigation capability. In addition to the SDR receiver and the inertial orientation unit, the described modalities can use accelerometers / tilt measurement devices, magnetic compass, microbarograph, oscillating in the return channel communication system, as well as automated rhythm devices / speed.

Multiple magnetic dipoles that rotate around an axis can be used to provide measurements that allow position calculations, without requiring a particular orientation of the receivers. A magnetic core antenna can be provided for an increased range of transmitters, so that bidirectional communications from surface to subsurface are permitted.

This and other features of the described embodiments will be better understood based on reading the detailed description that follows, in view of the figures, which form part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows the architecture of a positioning system.

Figure 2 shows a block diagram of a Radio Defined by Software receiver in accordance with a modality.

Figure 3 shows a transceiver in accordance with a modality.

Figure 4 shows a block diagram of a magnetic beacon transmitter.

Figure 5a shows a spherical core antenna and a horizontal loop antenna.

Figure 5b shows a stem core antenna.

Figure 6 illustrates an analysis of a positioning system in accordance with one embodiment.

Figure 7 shows an error analysis for the positioning system according to a modality.

Figure 8 shows the coverage of the transmitters when deploying in accordance with a modality.

Figure 9 shows a method of sub-surface digitalization in accordance with a modality.

Figures 10-1 1c show variations of a magnetic dipole. Figure 12 shows a field line of a magnetic beacon in polar coordinates.

Figure 13 shows a variation of a magnetic dipole.

Figure 14 shows a system according to a modality.

Figure 15 shows the interaction between a transmitter and a receiver.

Figure 16 is a table showing the relationship between the effective magnetic moment and a magnetic coil moment without core DETAILED DESCRIPTION OF THE INVENTION In the following detailed description, reference is made to the appended drawings, which form part of the present and show, by way of illustration, specific modalities in which the described modalities could be implemented. These modalities are described in sufficient detail to allow the person skilled in the art to implement the described modalities and it must be understood that other modalities could be employed, as well as that structural, logical and other changes could be made, without deviating from the spirit and scope of the modalities described herein.

An example of positioning system 10 is shown in Figure 1. The positioning system 10 comprises a series of components, which may include transmitters 12 (as used herein, the terms "transmitter" and "headlight" are interchangeable). ) and an SDR 14 unit ("receiver"). Additional opportunity signals 13, such as those of other transmitters in the very low / low / medium frequency range and AM radio signals, can also be exploited as additional sources of signals, as will be explained in more detail below.

Figure 2 shows a block diagram of a receiver 14. The receiver 14 comprises a three-component sensitive magnetic receiver that is capable of accurately detecting the magnetic field vectors emanating from the transmitters 12, a processing unit 15, an energy source 42, a GPS receiver 17, an inertial orientation unit 19, a magnetic antenna 31, a dipolar antenna 33, a signal processor 43, a VHF 45 transceiver, a land navigation system 47 and the sensors additional secondary 30 (eg, magnetic compass, accelerometers, tilt meters, microbarometer).

The processing unit 15 processes the data received by the three-channel VLF receiver 35, the dipolar antenna 33 and the secondary sensors 30 to provide a three-dimensional location of the receiver 14, either below or above the ground. The inclusion of the GPS receiver 17 allows the receiver 14 to interface with a GPS-based ground navigation unit and provide complete integration with the systems and databases of geographic surface information. The output 24 of the processing unit 15 can be configured in such a way that the existing terrestrial navigation options for the deployment and user interface are preserved and the underground locations are obtained from an easy transition of the positioning system 10 of the GPS locations determined using the times that the receiver 14 is above the land surfaces 5.

The processor 15 can also store reference locations of each of the transmitters 12, as well as the scan information on the opportunity signals 13. This data can be used to estimate the current position of the user. The GPS locations of the entry points are used to provide the "truth" for the starting positions. The outputs of the microbarometer (part of the secondary sensors 30) of the receiver 14 can also be used to provide an increasing update and correction of errors for the elevation estimates. Using this data, the calculated location can be updated continuously in the deployment output 24.

The magnetic fields induced by the transmitters 12 are detected by the magnetic antenna 31 of the receiver 14. A preferred magnetic antenna 31 for use with the receiver 14 is the Cube sensor Raytheon, a magnetic triaxial air coil receiver that is currently one of the most sensitive instruments available with a minimum noise floor of 10 kHz of 0.6 ftesla / square root Hz for the antenna of 30.48 centimeters and 5 ftesla / square root Hz for the antenna of 15.24 centimeters. The processing unit 15 operates a three-component VLF receiver 35 and a signal processor 43 for calculating the angle of deflection and the inclination of the vector magnetic fields induced by the transmitters 12. Using the known locations of the transmitters 12 and the Deviation angles with respect to the remote transmitters 12, the processing unit 15 determines the location of the receiver 14 continuously as the receiver 14 moves within the underground space.

The noise induced by the movement of the receiver 14 can potentially reduce the accuracy of the system 10 and, preferably, must be reduced below the minimum noise threshold of the system 10 for typical user movements. The frequency of operation can mitigate the undesirable noise, since the user noise components induced at the operating frequency are small. Taking this into account, the receiver 14 is designed so that the movement of the components in the very low frequency range of interest (preferably below 10 kHz, is minimal.) It should be understood that the method of taking into account said Design consideration could be implemented in various ways in accordance with the particular limitations of the receiver 14, which could be of a physical, electrical or aesthetic type For example, and in a non-limiting manner, the antennas 31, 33 may be covered by cushioning materials , eg, foamed rubber, which substantially attenuate the moving components in this range.This can be done with relatively small volumes of cushioning material.Also, the sufficient dynamic range at the outputs of the antenna 31, can be provided in such a way that noise induced by out-of-band movement (mainly in the extremely low frequency range), does not overload the electronic components. The inclination sensors (part of other sensors 30) can be included in the antennas 31, 33 to measure the movement of the antennas. The sensors of inclination in solid state based on micro-electromechanical sensors can be used for this purpose. With the appropriate movement information, the adaptation filtering can be used to further reduce the effects of movement on the antenna 31, 33. The Faraday complete protection of the antenna 31, 33 can be useful to reduce the potential interference of the antenna. outside interference Navigation in underground environments is possible by performing an embodiment of the system 10 which has transmitters 12 with two or more co-located magnetic dipoles with known magnetic properties (eg, frequency, amplitude and dipole orientation) or rotating dipoles (dipoles excited to a frequency determined with the dipolar direction rotating at a known speed around a known axis), as shown in Figures 11b and 11c. Rotary dipoles are preferred and comprise at least two dipole wires 2 with a modulated signal, such that the dipole magnetic moment rotates about a rotation axis 6, producing an associated amplitude signal that can be detected by the receiver. This approach allows the potential use of a smaller number of transmitters 12, which would also provide a more robust navigation solution. The above navigation schemes required at least three operational beacons 12. This mode allows navigation from a single VLF navigation beacon 12 comprising two or more co-located transmitting magnetic dipoles.

If the calibration of the magnetic antenna 31 and the VLF receiver 35 is known, as well as the magnetometer and the transmitter 12 are synchronized, the exact position of the magnetometer can be obtained from a single headlight 12 in an empty space. If the rotating dipole rotates in all three dimensions of a headlight 12, then the bearing in the overall coordinate system can be obtained by employing a single transmitter 12.

The location or navigation solutions for the rotary dipole mode can also be extended to co-located dipole modalities. As shown in Figure 10, a headlight of colocalized dipoles 12 is a headlight 12 comprising two or more oscillating magnetic dipoles that are actuated separately. The dipoles are located in such a way that their centers 3 are in the same point. The orientations of the magnetic moments 4 for each dipole, are different. A cube with three coils wrapped around its perpendicular faces is an example of a co-located dipole. A sphere with several coils is another example. The transmitter 12 may be based on a magnetic ferronucleus 44 (sphere, cube, etc., figures 5a and 5b) or may lack a core.

Figure 10 is an example of a co-located dipole beacon without core 12 based on two coils 2. The figure shows two colocalized dipoles. Two coils of wire 2 carry currents of two separate power supplies. The coils 2 are fixed in space, although the current in each of the coils 2 is modulated differently. For example, one coil 2 is driven at a frequency f1 and the other at a frequency f2 which produces an associated amplitude signal which can be detected by the receiver 14.

A rotating dipole headlight 12, like that shown in Figures 11a to 11b, is a magnetic dipole that rotates about an axis 6 in space. One embodiment includes a transmitter 12 with the axis of rotation 6 perpendicular to the orientation of the resulting magnetic dipole that rotates with a constant angular velocity. Figure 11a shows a magnetic beacon comprising a magnetic dipole that is rotated about an axis 6 perpendicular to its magnetic vector 4 (dipole magnetic moment). Figure 1 1b shows a magnetic beacon 12 with the field equivalent to that in Figure 11a. The two wire coils 2 are perpendicular to each other. The current source is modulated by a signal equal to the sine and cosine of the rotation phase. Figure 11c shows a light 12 capable of realizing the three-dimensional rotation of the effective magnetic dipole (three co-located dipoles).

A rotating dipole headlight does not have to have any movable part. For example, a headlight described in Figure 11b with two magnetic coils 2 perpendicular to each other, will produce the same field if the current source driving the two orthogonal coils 2 in Figure 11b is producing the currents defined by the following Equation 1: (????? = 'Rotation SGn (< P otación) l ^ Green = ^ Rotac i 0ii CO S (^> Rotation) "^ ^ where green and zui are the respective currents through the two coils 2 and Rotation is the current through the rotating coil, while (nulling is the rotation angle of the rotating coil.) Similar formulas can be derived for the headlights that comprise coils that are not orthogonal.

In a case of constant angular velocity, the equation defining said currents can be shown by Equation 2, as follows: 'Blue = Voting sin (wf) sin (fl / + F) = / Rfl ^ 10n (Cos ((0J + O)? 4- F) - COS (w - O) G - F)' vente = 'Rotation sen (wí) cos (f- / + F) = ¡Kot8ioa (8β? ((? + fl) t + F) 4- sen (w - O) G - F) (Ec.2) In other words, a rotating dipole is just a special case of a general co-located dipole. The complete three-dimensional rotation of the dipole is equivalent to 3 co-located dipoles (Figure 11c). In an equivalent formulation, the magnetic moment of the headlight is described with the following Equation 3: M = M .seu. (Flr + F) (Eq. 3) 0 where M = cosrof is the dipolar value, O and f are the frequency of rotation and phase, as well as? is the frequency of lighthouse transportation. For reasons of simplicity, the phase of the beacon carrier signal is specified at 0.

The co-located dipoles allow the bearing line (LOB) to be determined by a receiver 14 with an unknown orientation. To solve the LOB, 5 variables are determined: 2 angles with respect to the position of the receiver 14 in the magnetic dipole coordinate system (headlight) and 3 angles that determine the orientation and position of the headlight in the receiver's coordinate system 14 Theoretically, the distance can also be determined. The total geolocation requires the measurement of a sixth variable: the distance between the headlight and the receiver 14.

The measurements of the magnetic field produce three measurements by magnetic dipole in a transmitter beacon co-located 12. Therefore, any co-located beacon allows the determination of LOB in the coordinates of the receiver 14.

When a magnetic beacon is located at the origin of a Global Coordinate System (GCS) and the colocalized beacon is a rotating beacon with the dipole revolving around the z-axis 6 in the GCS, the value of the vector magnetic field in GCS is described by Equation 3 above. The magnetic field (B) of the dipole is determined through Equation 4, as follows: Therefore, the value of the magnetic field at a point r in GCC, where: X r = Y Z is expressed with Equation 5, as follows: B Global - - 3z2 sen. (Nf - 0) (Eq. 5) Figure 12 shows a magnetic beacon in polar coordinates.

The lighthouse is located at the origin of the X, Y, Z coordinate system. The unit of the receiver 14 is at the point of origin of vector B. The vector M of the dipole magnetic moment 4 denotes an instantaneous orientation of the magnetic moment of the lighthouse at a particular point in time. It shows the line of the instantaneous magnetic field 32 for the current position of the rotating beacon. The magnetic field line 32 intersects the position of the magnetometer. Magnetic moment 4 is excited by a coil magnetic field, e.g., 2, which operates at a fixed frequency below 10 kHz, at same time that revolves around the Z axis 6 at several dozen revolutions per minute. In a polar coordinate system defined by the receiver 14 as well as the center 3 of the dipole, the values of the magnetic moment 4 and the distance are defined through Equation 6, as follows: M cos (f2r + F - >) cos (9 M M sen (Hr + F - f) T ~ L M eos (fír 4- F - < >) sin # (Eq. 6) Where e ,, refers to a unit vector in the direction correspondent. Therefore, the magnitudes of the field components Magnetic B are defined through Equation 7, as follows: (Ec.7) The important characteristic of Equation 7 above is the fact that it separates the radial (r), angle of deviation (f) and inclination (3) dependence of the magnetic field. The square of the value of the magnetic field can be determined from Equation 8, in the following way: \ B \ = (^ 3) · (! + 3cos2 (nr + < í > - ¥ >) -cos2 (?) = = (^ j) - (1 + 1.5- cos2c? + 1.5 · cos2 (? · cos (2 · (O / + F - f))) = fUoM 2 3 (A \ = (^ 3) '4 3 + cos2 < 9 + (l + cos2 <?) | cos (2 · (O? + F -?)) (Eq.8) Note that the value of | 6 | 2 is independent of the actual orientation of the receiver 14. However, if the time dependence of | S | 2 is known, this provides sufficient equations to solve the distance (/ "), angle of deviation { f) and inclination (3) in the GCS system.

The LOB navigation in the receiver 14 / Local Coordinate System (LCS), by its acronym in English) can be done using this modality. The receiver 14 measures the instantaneous values of the magnetic field Bx, By, Bz. To determine the LOB of headlight 12, an orientation must be found in the LCS system where the time dependence of the corresponding components of the magnetic vector satisfies Equation 7. To find this orientation, the frequency of transport can be removed by adapting the field value magnetic in cosíyf yy change the frequencies by the value of?. As derived from this embodiment, the magnetic field values described are algebraic values of the modulation. The magnetic field values Bx, B, Bz are adapted in cos ¾ and siní2r, so apply the following Equation 9: B x = ax cos (Qr + < í >) + bx ßß? (O? + F) z = az cos (Qí +) + bz 8ß? (O? + F) (Eq. 9) The defined factors are the following: Vo = a and W ° = The angles a and ß are found to define the rotation of the magnetic field detector using Equation 10, of the following way: rot, = (Eq. 10) so that the new y-axis is parallel to the plane of rotation of the magnetic dipole when Equation 1 1 is satisfied, as follows: V '= rot¡| Vo W¡ = rot¡| W ° and the angle? is determined by Equation 12 of the Following way: cozy 0 seny rot¡¡ = 0 t 0 -seny 0 COSy (Eq. 12) so that the new x axis looks towards the transmitter 12, so that Equation 6 is satisfied, in the following way: (Vi¡ - rot¡¡| V \ W¡¡ = rot¡¡| W¡ Vf '+ wf + 4 · V 2 + 4 · wf = 4 · vf + 4 · wf (Eq. 13) The following Equation 14 is calculated: * 2 yi Z2 = rot¡¡ · rot¡ 3 yi ¾ (Eq. 14) where the vector: look towards the transmitter in the Local Coordinate System. Once these two adjustments are made, the address to receiver 14 can be calculated in the beacon coordinate system by noting that the vector: - 2- (i '') 2 + (Wj ') 2 (Eq. 15) in the Global Coordinate System it looks towards the receiver 14. The vector D is not unitary and can be normalized so that: _ D D0 = - \ D \ (Eq. 16) Equation 13 is true after the rotation is applied. Therefore, it must be determined whether the adjustment described in Equation 9 and 10 should be made after applying Equation 12 to the measured fields of the Equation 9, as in the following Equation 17: To determine the LOB of the receiver 14, an orientation is found in the GCS system where the time dependence of the corresponding vector components of the magnetic field of the associated amplitude signal satisfies Equation 7. To find this orientation, the frequency of transportation by adjusting the value of the magnetic field in costrix and sinwí and changing the frequency by the value of?. The instantaneous values of the strength of the square magnetic field can be calculated using Equation 18, as follows: B \ 2 = \ B X \ 2+ \ B \ 2+ \ B Z \ 2 (Eq. 18) The value of the out of the magnetic field is adjusted in cos t and s'm t, so that Equation 19 is satisfied, as follows: \ B l2 = c1 COS (2í "á + 2 I>) + C2 sin (2Q + 2) + c3 (Eq. 19) The values of the angle of deviation (< j >) and inclination (9) in the GCS system can be determined using Equation 20, of the Following way: The value of C3 in Equation 19 above can not be determined exactly in a Noisy environment, even if the integration is made over a long time. The value of the ratio of C1 and C2 is somewhat less susceptible to noise. In this environment, a dual rotating beacon, such as that shown in Figure 13, can be introduced so that its magnetic moment 4 (or its associated signal) is defined through Equation 23, as follows: M = | The headlight shown in Figure 12 is capable of producing a magnetic moment 4 as described for M by Equation 23 above. Using Equations 8 and 18 through 20, the deflection angle values can be derived in the coordinate systems defined independently by M1 and M2. The value of the deviation angle in the coordinate system M2 of FIG. 13 is the inclination in the coordinate system M1 and vice versa. Figure 13 shows a rotating beacon and moments related magnetic 4, which rotate independently in the XY and YZ planes.

To detect the magnetic moments 4 of Figure 13 separately, only one of the two frequencies (of transportation and rotating) that characterize each of the magnetic moments must be different. For example, they could have the same frequency of transportation if the rotation frequencies are different. Conversely, they could have the same rotation frequency, if desired It is important to know if the receiver 14 is calibrated and the amplitude of the headlight 12 is known, if the T phase of the headlight 12 is known and if the receiver 14 is synchronized and, based on it, what can be determined. If the receiver 14 is calibrated and the amplitude of the headlight 12 is known, as well as if the phase of the headlight 12 is known and the receiver 14 is synchronized, the exact position of the receiver 14 in the GCS system can be determined. If the receiver 14 is not calibrated or the amplitude of the headlight 12 is known, but the phase of the headlight 12 is known and the receiver 14 is synchronized, then the bearing of the receiver 14 in the GCS system can be determined. If the receiver 14 is not calibrated or the amplitude of the headlight 12 is not known, as well as if the phase of the headlight 12 is not known or the receiver 14 is not synchronized, the bearing of the receiver 14 in the LCS system can be determined .

Using a system 10 such as that shown in Figure 14, it can be derived that a headlight 12 with three or more co-located dipoles provide bearings in the GCS system and a rotary beacon 12 is not required. In this embodiment, when a single rotary dipole is used per headlamp 12, the deflection angle to the receiver 14 at the coordinates of the headlight 12 can be determined. Three headlights 12 with non-parallel headlights Z 6 are used for triangulation. When multiple (2 or more) rotating dipoles are used per transmitter 12, the entire LOB can be determined up to receiver 14. This uses two beacons 2 to perform the triangulation, wherein one of them can be a single rotating dipole. With a headlight 12 adjusted in an active manner, the headlight 12 rotates around the orientation of the receiver 14 and a communication channel is used. There, the orientation of the headlight 12 tracks the receiver 14 in search of a higher signal-to-noise ratio and the complete LOB can be determined up to the receiver 14. As such, two headlights 12 are employed to perform the triangulation and an energy is employed total less than for the configuration of the multiple rotating beacon 12.

In another embodiment, the need to provide the receiver 14 with an independent time-based synchronization with the transmitter 12 for scalar magnetometric navigation of the bearing line using co-located rotating magnetic dipoles is eliminated. In this embodiment, two magnetic dipoles rotate around the same axis 6 and it is possible that only two magnetic coils 2 are used. Said embodiment can be considered by adding a second coil 2 to the mode shown in figure 11a, so as to cause two dipoles rotate around axis 6, although the phase of the signals is at different pulse frequencies. The phase of a signal at the different pulse frequencies generated by the two rotating dipoles is independent of the position and orientation of the magnetometer and can thus be used as a clock signal. Additionally, in addition to using the twin magnetic dipoles for clock synchronization, they could also be used for navigation.

To measure the angle between the actual parts of the magnetic fields described above, each of the transmitters 12 and receivers 14 must be provided with highly accurate and stable timing mechanisms (part of the GPS receivers 17, 18 or other sensors 30). ), which are then synchronized to each other at the beginning of the period of interest. Figure 15 shows how the receiver 14 can intercept the magnetic field lines 32 of the signal resulting from the magnetic dipoles of a headlight 12 based on the measurements of the angle of deviation 7, the inclination 8 and the magnetic field.

In an environment where the conductivity is high, synchronization with a pulse frequency could be used to compensate for errors related to the effects of temporal propagation (between transmitters 12 and receiver 14). The magnetic field of two magnetic moments (M) with the same modulation frequency? rotating around the Z6 axis with frequencies and O2 is described through the following Equations 24 and 25: (Magnetic moment equation) Micos (it +?) + M2cos (n2r + F2) M i of ?? (O? I 4- F?) + M sen (ñ2t + F2) • COSCc or (Eq.24) (Magnetic field equation) In latitude / longitude coordinates, the field values are determined through Equation 26, as follows: Correspondingly, the value of the field square magnetic B is determined by Equation 27, as follows: B +? - f)) + + Ténnino 1 )) ++ Tenor 2 2 ^ -cos2 (? + 1 j + M2 ^ - cos2 (? + 1 ++ Tennino 3 My 2cos2c? · Cos (ÍV + F1 + O2? + F2 - Tennino 4 My 2 (3cos? (? + 2) · cos (ÍV - ¿+ F. Tennino 5 (Eq. 27) With respect to the above terms 1, 2 and 4 (Equation 27), each of them, or all of them together, can be used to determine the deviation angle f of the magnetometer. The first Term (or its equivalent Second Term) is used to determine the deviation angle in the case of the transmitter 12 comprising a single rotary beacon 12. The fourth term is very similar to the first two Terms, except that it is a frequency of pulsation. The fifth term, the difference of the pulse frequency, is independent of the angle of deviation.

The difference term of the pulse frequency could be used for synchronization as a clock signal. Since the phase value of that Term is independent of the angle of deviation, its phase can be used as a clock to determine the departure moment of navigation. In an environment where the conductivity is high, synchronization with a pulse frequency could be used to compensate for the effects of temporal propagation, since the delay in the detection of the signal from the fifth term is very similar to those for Terms 1, 2 and 4.

The terms of the sum and difference of the pulse frequencies could be used to determine the elevation. The proportion of the amplitudes of the last two terms depends on the elevation only and is expressed through Equation 28, as follows: Term 4 3cos & Term 5 3cos2 (3 + 2 _ nn ^ (Eq. 28) The ratio is independent of both the angle of deviation and the distance. Both of these terms can be measured in a noisy environment. Normally, the amplitude ratio is expected to be noisier than the phase measurement. Unlike in the case of a single rotating beacon, however, none of these terms is measured at a fixed frequency (2a>), but are equivalent to measuring the difference of the signals at two different frequencies around 2 ?.

In another embodiment, the receiver 14 can also incorporate an integrated return channel communication path that allows the user to maintain elementary communication throughout the length and exterior of the underground location linked to traditional communication systems located near the point Of income. As shown in Figure 3, one modality uses ad hoc transceivers interconnected in miniature, disposable mesh, which can be easily hidden 36 for this purpose.

The network interconnect protocol can be configured to allow automatic networking, transmission and updating using the receiver 14 and the transceivers 36. A base radio transceiver of 2.4 GHz 36 measures less than 21 x 27 x 6 mm, including a antenna, or around the area of a postage stamp. In the operation, a user can drop or place these transceivers 36 as a path of "breadcrumbs" as you move along a tunnel or facility. When placed in equines or bottlenecks, the transceivers 36 are capable of communicating several hundred meters before another must be placed.

The VHF transceiver 45 (FIG. 2) of the receiver 14 may have a transceiver 36 embedded in its electronic components that communicates with the path of "bread crumbs". At the entrance to an underground area, a conventional communication transceiver (not shown) can be connected to a communication channel for the rest of the network that supports the operation. The transceivers 36 can send and receive data. The receiver 14 can be configured with methods for an operator to easily and quickly enter coded commands that can be communicated to and from the communication network. For this purpose, a small, portable or portable personal digital assistant can be used, or a similar user output device 24 or 16. It is also possible to send and receive voice communications either intermittent or continuous throughout the same. net. In addition, users are able to send their position to the rest of the operations team. Similarly, users are able to receive, through the same network, the locations of other users in a team as they report their positions with other recipients 14.

Referring again to Figure 1, the transmitters may be magnetic surface beacons 12 that provide a signal at different frequencies in the very low / low frequency range. Three to four of these transmitters 12 are generally preferred to support the receiver 14 of the positioning system 0, as in use in an underground space.

Figure 4 shows a block diagram of a transmitter 12. Each of the transmitters 12 comprises an energy supply 16, typically a battery pack capable of supporting the system for up to 30 or more hours, which can be extended with additional batteries , a processor 25, a very high frequency transmitter ("VHF") 27, a very low frequency transmitter ("VLF") 29, a dipolar antenna 20 and an antenna of magnetic loop 21. The transmitter 12 provides an adjustable frequency source detectable through the receiver 14. The GPS receiver 18 could be used by the processor 25 to determine the location of the transmitter 12 within a distance of one meter. The coordinates are transmitted to the receiver 14 as configuration data 23 before the receiver 14 is inserted into the space of interest, either above or below the ground. The transmission antenna 21 may be a simple wire coil or a more complex system employing a ferrite core. The transmitters 12 could be packaged for manual placement, for aerial launching or for vehicle mounting.

Referring again to Figure 1, when the receiver 14 is operated in an underground space of interest 50, varying amounts of soil, rock and floor elements of the surface 5 can be discarded between the transmitters 12 and the receiver 14. With In order to determine the output force of the transmitter 12 required for detection by the receiver 14 under such circumstances, an operator could assume a source of 1 Am2 and calculate the fields in the received location as a function of the frequency (2p?), depth (R) and conductivity of the earth (s). For a vertical magnetic dipole on the surface of the Earth 5, the fields are described for the quasi-static case where the distance from the transmitter 12 to the source is much smaller than a wavelength in the conducting medium (eg, the surface of the Earth 5). In this medium, constant propagation is determined using Equation 29: (Eq. 29) where μ and e are the permeability and permissiveness of the medium driver and? it is the propagation constant. By definition, the length of Wave (?) in the conductive media, is shown through Equation 30, as follows: 1/??? =? (Eq. 30) For the conditions of: 10 1 < s < lO ^ mhos 100 < R < 1000 meters 100 < f < 106 hertz The main component of the magnetic field in the walls of a tunnel at the location of the receiver 14 is the vertical magnetic field, determined by Equation 31 as follows: 3meyz p - ??? (Eq. 31) where m is the magnetic dipole moment in Amp-m2. Make some assumptions for the typical operating conditions: s = 10"3 mhos f = 10,000 Hz R = 100 and 300 meters Produces the following values for the Field Resistance at receiver 14: R - 100 n Hz = 1.5 x 105 ÍTesla R = 300 m, Hs, = 1.9 x 101 ÍTesla Again, the previous values suppose a dipole moment of transmission of 1 A-m2.

The sensitivity of the ELF cube base antenna of 15.24 centimeters for use in receiver 14 is from 6 ÍTesla to 10 kHz. Assuming that this sensitivity is tangential (SNR = 6dB), this modality can operate at 20 dB SNR and a band limit noise of 1 Hz to give a satisfactory dynamic system response. Calculating the desired resistance of the desired transmitter 12 shows that the dipole moments used are 1.6 x 10"3 Am2 at 100 m depth and 0.8 Am2 at a depth of 300 m These are resistances generated relatively easily in the range of 5 to 10 kHz For example, the battery-operated Zonge NT-20 TEM transmitter that controls a loop of 1 m2 can easily generate a dipole moment of 25 Am 2. Much larger moments can be generated if this transmitter uses a larger antenna.

Very low frequency magnetic headlamps (VLF) are used to implement the subsurface navigation systems described herein. These magnetic headlights are compact, make efficient use of energy and are powerful, generating a high magnetic moment with minimal energy. Figure 5a illustrates an example of a dipole antenna 20 and the horizontal loop antenna 21 of the transmitter 12 shown in Figure 4. The antenna 21 can have the following characteristics: an air core 44, 100 turns of 37 aluminum wires, two layers of thickness, 0.1 m radius and 0.26 m height. An antenna 21 of this configuration would weigh around 3.7 kg and would have an input impedance with 10 kHz of 1 + J48 O. To create a dipole moment of 1 A-m2, it would operate with an energy input of 0.3 amps at 15 volts or 5 Watts. An efficient energy amplifier, Class D, can be used to produce the control signal with acceptable levels of harmonic distortion and with efficiencies of 90%. Therefore, for about 6 Watts of battery power, the transmitter can provide a CW transmitter signal constant.

For a design that uses a 10 D cell L1SO2 primary bacterium that supplies 175 Watts-hour at 15 volts, the transmitter 12 can operate for more than 30 hours. The parameters of antenna 21 are not limited to the previous configuration, but could be configured to use optimization to minimize energy consumption and produce the highest transmitted dipole moment required. The design of the electronic components of the amplifier is clear and will not be discussed further in the present.

In order to increase the magnetic moment, in another embodiment, the antenna 20 can be designed using a magnetic core 44, instead of an air core 44. The magnetic core 44 can trigger the effective magnetic moment, with the advantage over a core based on air 44 that, unlike the number of turns of the wire 37, the magnetic core 44 starts both the magnetic moment (M) and the inductance (L) in the same proportion, as shown in figure 16. Magnetic permeability can be in the range of 10 to 50. This can be achieved by using a ferret core 44 of small diameter or a foam core 44 of large diameter with ferrite particles suspended therein. Based on the modeling of a single-turn magnetic coil with a diameter of 1,001 meters and a magnetic moment of 1 Am 2, the effective magnetic moment of a coil 37 with a spherical core 44 is expressed with Equation 32 as follows : Msfeclim = (Eq. 32) where M is the magnetic moment without the core 44 and μ is the permeability of the magnetic material. The calculated model follows the graph in figure 16.

The magnetic core 44 can be spherical, as shown in Figure 5a, or a cylindrical rod core 44 as the antenna 34 shown in Figure 5b. The magnetic core antenna 34 which includes a magnetic core 44, in particular a cylindrical stem core 44, can be used to provide bidirectional communication between the surface and the subsoil in the system 10. With said antenna 34 included in the receiver 14, As well as on the surface, the magnetic moment can be amplified to such a degree that it is possible to maintain a continuous communication. This allows a user of the receiver 14 to maintain continuous, bidirectional communication from surface to subsurface through system 0.

Figure 6 shows an elliptically polarized signal 28 and a diagram 26 of received signal strength versus the orientation of the antenna. The diagram 26 of the energy distribution shows a polarized signal elliptically sent by a transmitter 12 and received by a Raytheon Cube used as a receiver 14. Once the signals of the beacons 12 are received by the receiver 14, these can be processed to determine the deviation angle of the vector of the primary magnetic field of each of the transmitters 12, as they are received. Each channel corresponding to the transmission frequencies of the antennas 21 on the surface, can be processed in this way to determine the solid angles between the vector fields of each of the transmitters 12. In addition to the signals of the surface transmitters 12 , other opportunity signals 13 (figure 1), such as navigation beacons, very low frequency communication systems, as well as the High Frequency Active Auroral Research Program (HAARP), can be used to provide Additional information about the location.

The location accuracy of the system 10 is affected by the ability of the receiver 14 to accurately understand and compensate for the propagation anomalies in the medium between the surface transmitters 12 and the receiver 14 when the receiver 14 is below the ground . Opportunity signals 13 can sometimes be used to characterize the medium (e.g., below surface 5). The distant sources of the opportunity signals 13 can basically produce uniform fields on the surface of the region around the operating area. These uniform fields can provide a source of signals that can be measured at the receiver 14. By accurately measuring these signals 13, the effects of inhomogeneity on the medium can be estimated. These effects can then be used to adjust the measured direction of the arrival of the signals from the surface transmitters 12, in order to accurately predict the location of the receiver 14.

In practice, the signals received may not always be as "clean" as shown in the example of Figure 6, since there may be a multi-way energy, as well as secondary magnetic sources induced. However, this apparent disorder can be discriminated from the primary field due to its signal characteristics and quadrature phase change. In order to further discern the location for the receiver 14, additional sensors 30 (FIG. 2) may be employed, as previously mentioned, with the receiver 14 to provide independent information either to directly identify the location or to assist in weighing the contribution of the signals of the headlight 12. The additional sensors 30 may include a magnetic compass, accelerometers / tilt meters, a microbarograph, which oscillates between the transmission channel return channel cards, as well as a pedometer for a version to be loaded by a single person and an odometer for a vehicle-mounted unit.

If, during a period of time in the underground operation, no signal is detected at all, the inertial guidance system 19 (FIG. 2) could provide location information updated several times per second. In this way, the receiver 14 could continue the operation during the moments in which the transmitters 12 are temporarily out of range or significant anomalies occur in the receiver 14 that distort the magnetic fields to have a negative impact on the calculated location. Another modality allows the use of magnetic fields for the location without requiring the use of an inertial navigation unit to orient the magnetic field sensor sensor of the receiver 14. If multiple sources of magnetic fields are available from the transmitter 12 of a known location and frequency, the magnetic field parameters can be measured independently of the orientation of the receiver 14, using the angles between the actual parts of the magnetic files created by each of the transmitters 12. This mode is well suited for use with the magnetic antennas 20, 21, 34 of ferrite core 44 shown in Figures 5a and 5b.

Although the inertial orientation system 19 is useful for situations in which the receiver 14 is outside the range of the transmitters 12, it is less reliable if it is completely dependent on it, sometimes providing erroneous coordinates due to the deviations. It also requires that the receiver 14 be properly oriented, which could be inconvenient at times. The magnetometer of the receiver 14 can be used as an additional location check during periods of use when the receiver detects the magnetic field of at least two transmitters 12. The receiver 14 measures a magnetic field in the coordinate system of its own body. Assuming that the Global Coordinate System and the body coordinate system are aligned, the receiver 14 can measure three component values (x, y, z) of the magnetic field H in accordance with the Equation 33, as follows: or for a pure sinusoidal signal, in accordance with Equation 34, as follows: However, the global and body coordinate system are not necessarily aligned. The relationship between these coordinate systems is described through a time-dependent rotation matrix of 3 x 3 Rot (t), so that receiver 14 actually measures H in accordance with Equation 35, as follows: (Eq. 35) where Rot (t) satisfies Equation 36, as follows: (Eq. 36) It is important to note that the square of the magnetic vector is independent of the orientation of the receiver 14, as shown in Equation 37 below: HMed T (- H Med H (t) HT { T) -H. { t) (Eq. 37) The variables can be extracted from the measurements of the square of the amplitude of the magnetic field (Equation 37). Assuming that the magnetic headlights of two transmitters 12 are generating the fields H1 and H2 at the location of the receiver 14 that can be described as: ?? = ??? · ?? 8 (??? + ??? · ^? (??? =? ß (?? ß '? 1?) (Eq. 38) The output of a receiver 14 exposed to the magnetic field (Equation 34) will still be described with Equations (36) and (37): H · sin (? A t) + H2R-COs ((ú2t) +? 2? · * ß? (? 2?)) Noise (Eq. 39) By combining the frequency terms of Equation 39, using Equation 40 below, it can be derived: (Ec.40) ^ Ht -H2 · 3ß? ((?? +? 2)?) ++ H i · H2- H i · H 9 - - - cos ((w1 + w2) r) ++ 2 ^ fl 2 2 __ "/ 2 IH + | H2 | -IH,] -1H2 | 2 ++ Riiido The coherent detection of double beacon frequencies and pulsation frequencies will recover the values of each of the terms in Equation 40. For example, by using Equation 41 that appears Then, one can retrieve the fifth and seventh terms of the Equation 40 2 2 f rT __r _ * H -72 -H¡-H2 'd J .t "-H (· / (G) · ?? 5 ((?? -? 2)? = - 2-- l- T J' o ° (Ec.41) Equation 40 does not allow a complete recovery of the vectors. Each of the vectors has 3 components for both real and imaginary parts. Therefore, there are 12 unknown variables in Equation 40 and only 8 sub-equations. However, Equation 40 allows the recovery of a very important value, that is, the cosine of the angle between the vectors of real parts of the magnetic field generated by the two transmitters 12 (1 and 2): The numerator of Equation 42 can be determined from Equation 40.

In an isotropic medium, the denominator of Equation 42 can also be recovered. There are eight sub-equations and eight unknown elements in Equation 40, in particular: , n? j * _ · tpi 2R TJ R jjl r R I In non-isotropic media, Equation 42 can be solved only approximately, but at sufficiently low frequencies, with sufficient accuracy.

Figure 7 provides an error analysis for the positioning system 10. This analysis assumes that there is a +/- 5o error in the measurement of the direction of the vector. Through integration and signal processing, it can be reduced to +/-. However, the geological effects and the presence of anomalous secondary radiators increase that uncertainty to approximately +/- 5o. Through the use of the precision frequency control, as well as the external synchronization of the transmitters 12 and the receiver 14 through the initial configuration data 23 and the communications from surface to subsurface or return channel, it becomes possible reduce this final uncertainty by an additional factor.

The positioning system 10 can use the potential distance, but the cooperative sources help to reduce the uncertainty in relation to the depth. Higher power transmitters 12 can be used to drive a scrambled frequency chirp signal or other multi-frequency signal. Due to the frequency dependence of the penetration depth of the electromagnetic waves in the ground, the antenna 31 of the 14 in the subsoil is capable of detecting the increased attenuation of the higher frequencies within the chirp signal and of providing, of this way, an additional limitation of the depth of the receiver 14.

The positioning system 10 can have a short set-up time, can be easily operated by field personnel and allows deployment throughout the world. System 10 consists of strong magnetic transmitters 12 (headlights) that operate in the very low / low frequency range. The system 10 can be supplied by air or manual means and is not affected by most of the nearby structures.

The deployment of the transmitters 12 can be done in several ways. The transmitters 12 can be dropped from the air through fixed-wing aircraft, rotating aircraft, or manually deployed. An all-terrain vehicle could be employed to place the transmitters 12 in the desired location, providing the optimal layout pattern. The transmitters 12 must be positioned in such a manner that at least three of the signals 40, 40 ', 40"overlap each other in the effective beacon range, as shown in Figure 8. To ensure coverage of the range of Transmitter 12 light, signal emissions 40, 40 ', 40"can form an umbrella throughout the target area 50.

To initiate the use of the positioning system 10, field personnel can synchronize their receivers 14 with the transmitters 12 by verifying the connectivity by displaying signals on their receivers 14. Once each of the transmitters 12 is placed and activated, these can be switched on and auto-located using a Global Positioning System (GPS). When the GPS system is blocked, the transmitter 12 can begin to emit location and orientation signals to the receiver 14 (Figure 1). The locations and orientation of the transmitter 12 are sent to the receiver 14 before entering an underground facility. The operator can ensure that the receiver 14 is initialized with the transmitters 12 before the subsurface, as well as that the tracking register is operational. An operations center located outside the site, but close to the application site, could be established to monitor the current position of the receivers of the positioning system 14 in the subsoil.

The receiver 14 of the positioning system 10 can be mounted on an all-terrain vehicle or carried in a backpack on the back. The receiver 14 can be configured in a way that can be loaded by a single person or in an ATV configuration. All necessary accessories are compatible with any of the configurations. The receiver 14 can display a current tier location, bearing, route tracking, critical points of interest in the way and battery life. The receiver 14 can be a platform based on a drop-down menu, with backlight, controllable by the operator. The menus can be designed to be easily navigated and easy to use for the user.

The transmitters 12 and receivers 14 can have an active life cycle of up to 30 or more hours of continuous operation, which can be extended with additional batteries. In the case that the field operations exceed the life cycle, the batteries can be replaced manually, or new transmitters 12 can be deployed. An internal memory battery 42 (FIG. 2) can prevent the loss of data from the receiver 14 in case of primary battery failure. In order to preserve the limit operational identification and power of the battery 16 of the headlight 12, a warning and time delay capability can be employed when the transmitters are deployed before operations.

A return channel communication link employing disposable transceivers 36 (figure 3) or bidirectional surface to subsurface communication employing magnetic dipoles 34 (figure 5b), they can be used to communicate with the surface transmitter / receiver, as well as other operational elements. These transceivers 36 can provide a line of visual data transmission along the tunnels, whereas magnetic dipoles 34 do not need to depend on it. The individual transceivers 36 can form a sparse network capable of transmitting data between units above the ground and below the ground. The receiver 14 may have the ability to send low speed data communications to the receiver above the ground. This may allow the remote control center to track the location of the receivers 14 of the underground positioning system and communicate with the operator of each of the receivers 14.

The navigation and generation of underground maps can be done in multiple ways. In the back pack configuration, a single operator can operate and transport the receiver 14 while exploring the underground environment. With the receiver 14 mounted on a vehicle, the operator of the vehicle can operate the positioning system 10 hands-free, while the data is sent to the receiver on the surface. The portable receiver 14 can be attached to the operator's equipment. The mobile control center may have the same geographical representation of the generation of underground maps and navigation as the underground operator.

Beyond geophysical exploration, other potential applications of the positioning system concept 10 include the remote exploration of abandoned underground mines, the exploration and investigation of natural caverns, as well as the rescue in underground caverns and mines, or other similar uses. In addition, this modality is not limited to underground applications, but can be applied to a whole series of environments, including previous land locations. In particular, another modality will now be described in detail.

In traditional geophysical exploration employing electromagnetic approaches, the presence of conductors near the source and receiver 14 can be minimized through careful harvest planning. However, in the positioning system 10, the operating sites could have surface conductors near the locations where the transmitters 12 are deployed. These conductors could have the shape of pipes, tunnel linings and drill holes could be present at all along the operated area. The site could also include underground conductors near the receiver field 14. For navigation purposes, all of these are problematic and represent a significant source of noise that could impede the proper operation of the positioning system 10. Preferred embodiments described herein can address all these functional elements: validation of theoretical models; development of magnetic field templates to support location algorithms; and development of automated procedures to separate the clutter from the direct signals transmitted.

For the positioning aspects of this system, this natural and man-made noise is a potential obstacle to the performance of the positioning system 10. In another embodiment of this system 10 shown in Figure 9, noise is actually a source of useful signal information that can be analyzed to reveal significant or important information about the composition of the materials and / or the hydrology of the land surface 5 within the volume of influence of the transmitters 12 of the positioning system 10. Various means are possible different to alter the behavior and operation of the positioning system 10 to conduct an investigation of the geophysical properties of subsurface materials.

VLF coherent magnetic hardening or strategic hardening (SIIF) facilities, as well as underground facilities (SHUF) provide an observer using system 10, information on the distribution of conductive materials and underground magnetic materials. The receiver 14 is capable of distinguishing a motor or generator from the stainless steel reactor or a large piece of communication equipment. The system 10 can also detect reinforced tunnels. The system 10 can provide detailed information on what is behind the radio frequency protection that can not be provided by the radar penetrating the ground. If the earth's surface 5 is too conductive for the radar to penetrate the earth to be useful, this mode allows the detection of both reinforced and non-reinforced tunnels.

The VLF coherent magnetic digitizer is a combination of two or more vehicles 101 and 102, as shown in Figure 9. Multiple transmitters 12 in the extremely low / very low / low frequency ranges, are employed as the magnetic field beacons of radio frequency. Depending on the desired information and the availability of specific access, similar transmitters 12 are also used within the underground space and in vertical and / or horizontal drilling wells. For geophysical applications, the transmitters 12 can transmit signals either from a single frequency, eliminated frequency or some other signal mode to simultaneously maximize the determination of the location for the receiving units 14 and provide improved data to support the geophysical interpretations. The locations and orientations of the transmitter 12 are passed by a radio frequency link to a receiver 14 in the form of configuration data 23 before the receiver 14 goes to the sub-floor. The underground receiving unit 14 again comprises a three-component receiver for detecting the transmitters 12, other sources of extremely low / very low / low frequency, as well as similar signals. The underground receiving unit 14 can also be used above the floor and / or in vertical or horizontal drilling wells to improve geophysical identification collections. Additional geophysical sensors can be deployed simultaneously to aid in interpretation.

The two or more vehicles (eg, remote-controlled aircraft or surface vehicles) 101 and 102 carry a magnetic transmitter 12 and a receiver 14. A transmitter 12 is mounted on a first remotely piloted aircraft 101 and a receiver 14 is mounts on a second remote piloted aircraft 102. The receiver 14 measures the magnetic field values over a large area and attempts to measure the equivalent values of the induced fields 103, 104 generated by the underground objects at the site of interest . The induced fields are related to the volume of magnetically active materials and, therefore, the size and positions of the underground objects 105, 106. The vehicles traverse the space above the site of interest to be digitized. The transmitter 2 generates a magnetic dipole reference field with an extremely stable frequency, e.g., synchronized with the GPS system and a well-characterized magnetic field distribution. The receiver 14 measures the in-phase and quadrature values of the three components of the magnetic field. All measurements are made at frequencies around 1 kHz. The measurements are solved to determine the distribution of the equivalent underground magnetic sources. The phase sources correspond to magnetic materials, e.g., engine generators. Quadrature sources correspond to conductive materials, such as aluminum structures, cables, and so on.

This modality questions the conventional protection techniques. The frequency of 1 kHz makes the system relatively insensitive to bad driving elements, such as reinforced concrete, minerals with a high water content, and so on. Conventional protection techniques such as 1.6 mm thick copper sheet will not prevent the probe from using system 10 with a very low frequency, as described above. A user of system 10 in this manner could increase the sensitivity to conductive materials by increasing the frequency. Conversely, the user could reduce the frequency to decrease the sensitivity to the environment. The use of primary frequencies below 10 kHz also minimizes potential interference from naturally occurring sources, such as distant light storms that produce reduced levels of noise in this frequency range.

This technique is different from geological magnetic sounding, because it does not attempt to measure the distribution of the magnetic properties of subsurface materials. At very low frequencies, the primary and secondary magnetic fields could be easily separated. The eddy currents induced are orthogonal (in quadrature) with respect to the magnetic field. Therefore, the secondary magnetic field that they generate is in quadrature with the primary field. If the latter is small and tertiary effects can be disregarded (ie, low frequency or low conductivity), phase or quadrature field measurements can separate the primary and secondary magnetic fields and, therefore, the perturbations caused by the materials ferromagnetic, eg, steels, as well as conductive materials, eg, copper and aluminum, can be detected.

The processes and devices described above illustrate the preferred methods and the typical devices of the many that could be used and produced. The description and the foregoing drawings illustrate the embodiments that achieve the purposes, features and advantages of the present invention. However, it is not intended that the present invention be strictly limited to the embodiments described and illustrated above. Any modification, although not predictable at the present time, of the present invention that is within the spirit and scope of the following claims, should be considered as part of the present invention.

Claims (50)

NOVELTY OF THE INVENTION CLAIMS

1. - A navigation system comprising: at least one transmitter comprising at least two magnetic dipoles, said transmitter being configured to generate a magnetic field; and a receiver comprising a magnetometer configured to receive inputs from said at least one transmitter.

2 - . 2 - The navigation system according to claim 1, further characterized in that the transmitter is configured to change the respective amplitudes of the magnetic dipoles in accordance with one or more predetermined patterns, thereby producing associated signals.

3. - The navigation system according to claim 2, further characterized in that the amplitude of a first magnetic dipole is changed in accordance with a first pattern and the amplitude of a second magnetic dipole is changed in accordance with a second pattern, wherein the first pattern is different from the second pattern.

4. - The navigation system according to claim 2, further characterized in that the receiver is configured to identify each transmitter based on the differences between their associated signals.

5. - The navigation system according to claim 1, further characterized in that the transmitter is configured to change the amplitudes of the magnetic dipoles at a constant frequency with respect to time.

6. - The navigation system according to claim 2, further characterized in that the transmitter is configured to change the amplitude of a first magnetic dipole to a first frequency and the amplitude of a second magnetic dipole to a second frequency, wherein the first frequency is different from the second frequency.

7. - The navigation system according to claim 2, further characterized in that the transmitter is configured to change the associated signals in accordance with a predetermined pattern.

8. - The navigation system according to claim 1, further characterized in that the transmitter is configured to change the orientation of the first magnetic dipole in accordance with a first pattern and the orientation of the second magnetic dipole in accordance with a second pattern, wherein the first pattern is different from the second pattern.

9. - The navigation system according to claim 6, further characterized in that the magnetic dipoles are configured to rotate about respective axes at a constant rate.

10. - The navigation system according to claim 9, further characterized in that the associated signals are configured to rotate in a fixed plane.

11. - The navigation system according to claim 10, further characterized in that the receiver is configured to determine a bearing of the transmitter based on an orientation of the fixed plane.

12. - The navigation system according to claim 9, further characterized in that the receiver is configured to determine the line of the bearing to the transmitter based on the orientation difference between at least the first magnetic dipole and the second magnetic dipole.

13. - The navigation system according to claim 12, further characterized in that the receiver is configured to determine a distance to the transmitter based on the amplitude signals of the magnetic dipoles.

14. - The navigation system according to claim 1, further characterized in that the transmitter is configured to change the orientations of the magnetic dipoles at different respective frequencies.

15. - The navigation system according to claim 14, further characterized in that the transmitter comprises In addition to a first clock, the receiver further comprises a second clock, further characterized in that the first and second clocks are synchronized to be used in signal detection.

16. - The navigation system according to claim 15, further characterized in that the receiver synchronizes the second clock with the first clock based on a difference in the orientations of the magnetic poles.

17. - The navigation system according to claim 1, further characterized in that the magnetic dipoles are rotating dipoles.

18. - The navigation system according to claim 1, further characterized in that the magnetic dipoles share a center of rotation.

19 -. 19 - The navigation system according to claim 1, further characterized in that the transmitter additionally comprises at least two non-coaxial magnetic coils for generating the magnetic field.

20. - The navigation system according to claim 1, further characterized in that the transmitter additionally comprises at least three non-coaxial magnetic coils for generating the magnetic field.

21. - The navigation system according to claim 20, further characterized in that at least one of the magnetic coils includes a magnetic core.

22. - The navigation system according to claim 21, further characterized in that the at least two magnetic coils share the same magnetic core.

23. - The navigation system according to claim 1, further characterized in that it further comprises a device for determining a line of the bearing of the receiver with respect to the transmitter.

24. - A navigation system, comprising: a transmitter comprising at least two co-located rotating magnetic dipoles, two co-located magnetic dipoles sharing a rotation axis; and a receiver comprising a magnetometer.

25. - The navigation system according to claim 24, further characterized in that said at least two co-located magnetic dipoles are generated by two or more magnetic coils.

26. - The navigation system according to claim 24, further characterized in that said receiver is configured to use a signal produced by the two rotating magnetic dipoles co-located as a clock signal.

27. - The navigation system according to claim 24, further characterized in that the receiver is configured to use a signal produced by the two rotating magnetic dipoles co-located to obtain a line of the bearing with respect to the transmitter.

28. - A system for transmitting signals between a top surface and underground locations, which comprises: a transmitter comprising a first magnetic antenna with a magnetic core; and a receiver comprising a second magnetic antenna.

29. - The system according to claim 28, further characterized in that said magnetic core comprises a cylindrical rod-shaped core.

30. - The system according to claim 28, further characterized in that said magnetic core comprises a ferrite core.

31. - The system according to claim 28, further characterized in that said magnetic core comprises a foam rubber core embedded with ferrite particles.

32. - The system according to claim 28, further characterized in that at least one of said transmitter and receiver comprises a magnetometer.

33. - The system according to claim 28, further characterized in that said magnetic core comprises a spherical core.

34. - A system for performing subsurface scans, which comprises: a transmitter comprising a magnetic dipole that produces a primary magnetic field; and a receiver sensitive to quadrature and phase values of the primary magnetic field and which is sensitive to secondary magnetic fields induced by the primary magnetic field.

35. - The system according to claim 34, further characterized in that it additionally comprises a global positioning system synchronized with said transmitter.

36. - The system according to claim 34, further characterized in that the primary magnetic field has a frequency below 10 kHz.

37. - The system according to claim 34, further characterized in that the transmitter is provided in a first mobile vehicle and the receiver is provided in a second mobile vehicle.

38. - A method for determining locations, which comprises: transmitting a signal with at least two co-located magnetic dipoles; receive the signal with a receiver; and determining the location of the receiver with respect to the at least two colocalized magnetic dipoles using triangulation.

39. - The method according to claim 38, further characterized in that said at least two co-located magnetic dipoles are rotating dipoles.

40. - The method according to claim 38, further characterized in that said at least two colocalized magnetic dipoles share a center of rotation.

41. - The method according to claim 38, further characterized in that said at least two colocalized magnetic dipoles have magnetic cores.

42. The method according to claim 38, further characterized in that it further comprises determining a bearing line from the magnetometer to the at least two co-located magnetic dipoles.

43. - The method according to claim 38, further characterized in that it comprises adjusting at least one of the frequency of transport and frequency of rotation in at least one of the at least two co-located magnetic dipoles.

44. - The method according to claim 38, further characterized in that the two co-located magnetic dipoles are rotating and share an axis of rotation.

45. - The method according to claim 44, further characterized in that it further comprises using the two rotating magnetic dipoles co-located as a clock signal.

46. - A method for performing communication between the upper surface and the underground locations, which comprises: transmitting a low frequency signal using a first antenna with a magnetic core; and receive the signal using a second antenna.

47. - The method according to claim 46, further characterized in that said magnetic core comprises at least minus one of a cylindrical stem core, a spherical core, a ferrite core and a foam rubber core embedded with ferrite particles.

48. - A method for subsurface digitalization, which comprises: transmitting a low frequency primary magnetic field using a magnetic dipole; and detect the quadrature and in phase values of the primary magnetic field and as secondary magnetic fields induced by the primary magnetic field.

49. - The method according to claim 48, further characterized in that the primary magnetic field has a frequency lower than 10 kHz.

50. - The method according to claim 48, further characterized in that it comprises transmitting the primary magnetic field from a first mobile vehicle and detecting the secondary magnetic field in a second mobile vehicle.